The objectives of this project are to produce endothelial linings (pseudointimas) in standard artificial vascular prostheses, to determine the long term stability of such surfaces, and to assess factors affecting their development. For these experiments endothelial cells will be derived from jugular veins of dogs and autologously seeded into double velour dacron or expanded teflon 6mm X 30cm thoracoabdominal bypass grafts during preclotting procedures. Some vessels will be seeded immediately after the derivation of the cells, while others will be seeded after the cultivation of cells for 2 weeks with and withut mitotic stimulants. Grafts will be harvested after implantation for periods of 1 day to 1 month to monitor the early healing response as well as after 1 year to study long term stability. Supporting experiments will determine the optimal method for seeding cells into the teflon prostheses and the effects of thrombocytopenia, aspirin and dipyridamole on endothelization of the grafts. Scinti-scanning of the grafts and assessment of platelet survival using 111 Indium will be used to non-invasively monitor endothelizaion. Grafts will be evaluated grossly, and by light, transmission and scanning electron microscopy to determine the thickness and character of the intimal lining. Factor VIII related immunofluorescence and electron microscopy will be used to verify the presence of true endothelium.